In view of the extra-large hydropower project, geophysical detection holes are arranged on the left slope of the spillway tunnel outlet to detect the wave velocity and relaxation of rock mass. Combined with mechanical parameters of geological rock mass, based on the analysis of deformation monitoring data of slope rock mass, the mechanical parameters of slope rock mass and structural plane are obtained by using incremental displacement intelligent inversion method, and the unloading relaxation effect of rock mass and rock mass quality are further analyzed. On this basis, the displacement and stress characteristics of slope rock mass after excavation are simulated and calculated by finite element method, and the deformation and quality status of slope rock mass are analyzed, which provides reference for judging the stability status of slope and long-term safe operation of hydropower projects. It has certain practical guiding significance.